As dog and cat ownership has expanded to nearly 2 out of 3 American households and spending on pet pampering products has exploded, Bay Area residents have taken to giving their animals more human-sounding names - such as Max, Lucy, Samantha, Charlie or, in the case of one San Francisco papillon spaniel, William III.

But the most commonly loved pet of all, according to a Chronicle review of more than 60,000 pet licenses, is a Labrador retriever named just plain Buddy. He lives in at least 89 different Bay Area homes, the data show.

The Chronicle looked at animal license records from San Francisco, Oakland and San Jose to find the most popular pet names - and the most perplexing.

The computer review showed that people are naming their pets like children. Seventeen out of the top 25 tags for dogs and cats are typical people names. Six pets were named Jennifer, seven Marcus and four Kevin.

Beagles are likely to be Bailey. Boxers often are Rocky. Dachshunds are Oscar. And Jack Russell terriers are, of course, Jack.

"That's been the trend for about 15 years, because nowadays pets are members of the family," said Lynn Spivak, who has worked as a San Francisco pet advocate for nearly two decades.

"Personally, I don't understand it," said Spivak, who first worked with the San Francisco Society for the Preservation of Animals and now is a part of Maddie's Fund, a new family foundation dedicated to saving the lives of shelter animals. "I like food names myself - like Honey, Peaches and Cookie."

Cute, classic pet names seem more likely to go to cats - Tiger, Tigger and, of course, Kitty. They also go to certain small dog breeds, like Lucky the Pomeranian and Princess the poodle. The ever-popular Chihuahua is likely to get stuck with such labels as Chico, Chiquita, Shorty and even Taco.

Then there are the wise guys. Twenty pets got dubbed Killer, including six Chihuahuas, three cats, a Pomeranian, a rat terrier and a dachshund.

The number of American households that own pets has jumped from 56 percent in 1988 to 63 percent in 2006, according to a survey by the American Pet Products Manufacturers Association. But spending on pets has more than doubled since 1994 - to more than $40 billion a year, according to the survey.

"A lot of this is being driven by Baby Boomers whose kids have gone off to college - they're looking for something to dote upon," said Bob Vitere, president of the association, who said he has seen an amazing array of luxurious pet products and services emerge, from cell phones that allow you to call your pet over a collar speaker phone to companies that will scoop up the poop up in your backyard.

No one seems to adore their animals more than residents of the Bay Area, which was ranked as the nation's "Most Humane" metropolitan area last year by the American Humane Society.

That adoration is on full display daily at the nation's largest off-leash romping ground for dogs and their people - Point Isabel Regional Shoreline Park in Richmond.

There this week, a Pomeranian named Lulu traded sniffs with a Hungarian vizsla, whose owner had dubbed him with the "regal but not ostentatious name" of Jackson. Meanwhile, a shaggy mix named Sweet Jimmy playfully nabbed a slimy rubber ball that had been dropped by a nearby Tibetan terrier.

"Jimmy, sweetheart, that's not yours," called out doggy "dad" Michael Valladares of Albany, who admits he's one of those childless dog lovers who treats his pet just like a kid.

"He was named Noodle when we got him, but it wasn't long before we knew that Noodle wouldn't do," said Valladares, 38, a graphic designer. "We find that a lot of dogs have adult names, not cute dog names. Jimmy has friends named Larry and Jackson."

Betty Fong, 46, of El Sobrante looked on this scene from the nearby Sit and Stay Cafe, where humans can grab a mocha for themselves and a doggy ice cream for their pups. She admitted she sometimes finds it confusing.

"When you hear people calling out these names, sometimes you wonder whether they're calling their dog or their child," she said.

Pet licenses are by no means a complete census of all Bay Area pet names. Licensing agencies acknowledge that only about 15 percent of dog owners obtain dog licenses. For cats, which are not required by law to obtain licenses, the figures are even lower.

Still, the top Bay Area names are similar to those reported by national pet tag companies that keep statistics on pet naming trends.

While cats are not as prominent in the licensing data - or at the dog park - they have quickly become the favored pet for many Bay Area families, according to San Francisco Animal Care and Control Director Carl Friedman.